In this study, quaternary titanium–niobium–zirconium–tantalum (Ti–Nb–Zr–Ta) alloys were designed an‎d fabricated as biocompatible alternatives to the conventional Ti–6Al–4V alloy using the spark plasma sintering (SPS) technique. The primary objective of this research was to eva‎luate the influence of varying alloying element contents on the microstructure, mechanical behavior, an‎d corrosion resistance of the fabricated samples. For this purpose, two alloying series were investigated: one with varying tantalum contents (1, 5, an‎d 10 wt.%) an‎d another with varying zirconium contents (4, 7, an‎d 10 wt.%). High-purity elemental powders were mechanically alloyed an‎d subsequently consolidated by SPS under the conditions of 1100 °C, an applied pressure of 50 MPa, an‎d a holding time of 5 minutes. Archimedes’ density measurements revealed that all samples exhibited relative densities above 99.5%, indicating the high efficiency of the SPS process in achieving nearly fully dense, pore-free microstructures. X-ray diffraction (XRD) analysis confirmed the stabilization of the β phase in the presence of tantalum, accompanied by a reduction in the α-phase fraction with increasing Ta content. Scanning electron microscopy (SEM) observations demonstrated a homogeneous microstructure an‎d uniform elemental distribution, particularly in the Ti–35Nb–7Zr–5Ta composition. Microhardness testing indicated that increasing the tantalum content from 1 wt.% to 10 wt.% enhanced the hardness from approximately 350 HV to 400 HV. Furthermore, the addition of zirconium up to 7 wt.% improved phase uniformity an‎d enhanced fracture toughness. Tensile testing revealed a maximum ultimate tensile strength of approximately 900 MPa an‎d an elongation to fracture of around 6%, providing an excellent strength-to-modulus ratio suitable for biomedical implant applications. Electrochemical corrosion tests in simulated body fluid (SBF) demonstrated that the Ti–35Nb–7Zr–5Ta alloy exhibited the highest corrosion resistance, with a corrosion current density of about 51 nA/cm². Owing to its high relative density, low elastic modulus, favorable biocompatibility, an‎d the absence of toxic elements, this alloy can be considered a promising can‎didate for orthopedic an‎d dental implant applications.

رحمت اله عمادي

مسعود عطاپور , محمدحسين مصلي‌نژاد